What you want to do is have the car corner balanced. They'll put the car on four scales, figure out the cross weights, and raise or lower each side until balance is achieved. This is sort of the point of having coilovers.
It's normal for the front to be a little higher. Look at an M5. It really comes down to what level the spring hats are machined at. Mixing and matching suspension components is a trial and error process.